## Exergy and its Applications

Exergy analysis is an approach used by engineers to address the aspects of energy use or energy transformation that are governed by the second law of thermodynamics. While the first law of thermodynamics implies that heat and work are both forms of energy transfer, the second law implies that they are not equivalent. When heat transfer occurs, it is not just energy that is transferred: another quantity, entropy, is also transferred. When an amount of energy is transferred as heat, the corresponding amount of entropy transfer is inversely proportional to the absolute temperature at which the heat transfer occurs.

The implications of the second law of thermodynamics, some of which have been mentioned, are wide-ranging. Exergy analysis is a practical approach to evaluating the merit of energy conversion, or transmission or distribution processes and systems. Energy is conserved as a law of nature and therefore, for a cycle or a steady process, the energy output equals the energy input. Exergy (based on the Greek ‘ex ergon’, meaning ‘from work’) is the potential for doing shaft work in the context of an encompassing equilibrium environment. It cannot be created, but can be destroyed. For a cycle or steady process the exergy output will be less than or, at best, equal to the exergy input. The localization in space and time of where exergy destruction occurs thus localizes where the ‘potential for producing shaft work’ has been destroyed. Minimization of exergy destruction results in thermodynamic improvement and can be used as the basis for thermodynamic optimization in real situations where processes must occur at a finite rate or cycles must be completed in finite time. This latter concept, is newer than the original concept of exergy analysis and is commonly known as ‘finite time thermodynamics’.

The following publications involve, or relate to, exergy analysis and its applications. Where author names are in bold type, these were postgraduate students working with Jim McGovern.

**Peer-reviewed Journal Publications**

- McGovern, J., Thermodynamic Analysis of Closed Steady or Cyclic Systems. Entropy, 2015, 17, 6712-6742. doi:10.3390/e17106712, https://arrow.dit.ie/engmecdesignart/3/
- McGovern, James and Pierre Le Goff, 'Les termes de signes positif et negatif en analyses exergetiques des flux de chaleur', Revue Generale de Thermique, 35 (1996), 651-655. https://arrow.dit.ie/engmecdesignart/1/
- McGovern, J. A. and E. I. Yantovski, 'Mechanical work at a boundary and its associated exergy transfer', Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, 210 (1996), 541-547.
- McGovern, J. A.,
**Harte, S.**, 'An exergy method for compressor performance analysis', International Journal of Refrigeration, vol. 18, no. 6, 1995, pp. 421-433. - McGovern, J. A., 'Communication on 'Thermoeconomic optimization of a ventilation air heater in a backpressure combined heat and power plant' by T. J. Kotas and D. S. Kibiikyo', Proc. Instn. Mech. Engrs., vol. 204, part A, 1990, li. 281 (with reply by Kotas & Kibiikyo, pp. 281 & 282).
**O'Toole, Francis**and James A. McGovern, 'Some concepts and conceptual devices for exergy analysis', Proc. Instn. Mech. Engrs., part C: Journal of Mechanical Engineering Science, vol. 204, 1990, pp. 329-340.- McGovern, James A., 'Exergy analysis - a different perspective on energy; Part 1: the concept of exergy', Proc. Instn. Mech. Engrs., vol. 204, Part A, 1990, pp. 253-262.
- McGovern, James A., 'Exergy analysis - a different perspective on energy; Part 2: rational efficiency and some examples of exergy analysis', Proc. Instn. Mech. Engrs., vol. 204, part A, 1990, pp. 263-268.
- McGovern, James A., 'Exergy analysis - a different perspective on energy; Part 1: the concept of exergy', Transactions of the Institution of Engineers of Ireland, vol. 114, 1989-1990, pp. 181-212.
- McGovern, James A., 'Exergy analysis - a different perspective on energy; Part 2: rational efficiency and some examples of exergy analysis', Transactions of the Institution of Engineers of Ireland, vol. 114, 1989-1990, pp. 213-228.
- McGovern, J. A. and
**F. O'Toole**, 'Discussion on 'Approximate analyses of feed and heating cycles for steam combined heat and power plant' by J. H. Horlock', Proc. Instn. Mech. Engrs., vol. 202, no. A3, 1988, pp. 211-213.

**Conference Publications**

- McGovern, J. A. and
**Oladunjoye, S.**, Non-intrusive second law performance evaluation of a domestic freezer in Proceedings of the 8th International Conference on Sustainable Energy and Environmental Protection—Part 2: State of the Art on Environmental Protection, Olabi, A. G. and Alaswad, A. (Eds.), University of the West of Scotland, Paisley, PA1 2BE, UK, August 2015, pp.48–53, https://arrow.dit.ie/engmecdesignconf/3/ **Georgiana Tirca-Dragomirescu**, Monica Costea, Michel Feidt, Jim McGovern, Alexandru Dobrovicescu, Diana Tutica, Abdelhamid Kheiri, ‘Modeling and Optimization of Heat Exchangers Within Gas Turbine Systems’, ASME 2012 11th Biennial Conference on Engineering Systems Design and Analysis, Volume 2: Applied Fluid Mechanics; Electromechanical Systems and Mechatronics; Advanced Energy Systems; Thermal Engineering; Human Factors and Cognitive Engineering, Nantes, France, July 2–4, Paper No. ESDA2012-82672, American Society of Mechanical Engineers, 2012, pp. 699–708.- Jim McGovern,
**Georgiana Tirca-Dragomirescu**, Michel Feidt, Alexandru Dobrovicescu, ‘A Critical Exploration of the Usefulness of Rational Efficiency as a Performance Parameter for Heat Exchangers’, ECOS 2012 The 25th International Conference on Efficiency, Cost, Optimization and Simulation of Energy Conversion Systems and Processes, Perugia, June 26th-June 29th, Firenze University Press, 2012, pp. 13–23 **Dobrovicescu, Alexandru**, Michel Feidt, Lavinia Grosu, Jim McGovern and Georgiana Tirca-Dragomirescu, ‘Analyse du comportement réel et de l'optimisation structurelle des cycles de turbines à gaz’, Congrès Français de Thermique SFT2011, eds. F. Bataille and G. Flamant, Perpignan, France, 24–27 May, 2011, Vol. 2, pp. 801–806. https://arrow.dit.ie/engschmeccon/44/- McGovern, James A. Le Goff, Pierre, 'Les termes de signes positif et negatif en analyses exergetiques des flux de chaleur', Actes des 4 es Journees Europeennes de Thermodynamique Contemporaine, 27-29 September, Nancy, France, CERET, CNRS, INPL, Universite Henri Poincare, 1995, pp. 319-326. https://arrow.dit.ie/engmecdesignart/1/
- McGovern, James A., 'Thermodynamic relations for chemical exergy or calorific values with respect to non-standard reference temperatures or pressures', Thermodynamics and the Design, Analysis, and Improvement of Energy Systems, ed. R. J. Krane, ASME, AES-vol. 33, 1994, pp. 299-303.
- McGovern, James A.;
**Harte, Shane**; and Strikis, Guntis, 'Real gas performance analysis of a scroll or rotary compressor using exergy techniques', Proc. 1994 International Compressor Engineering Conference at Purdue, ed. Werner Soedel, West Lafayette, Indiana, Purdue University, vol. I, 1994, pp. 193-198. - McGovern, J. A. and
**Murphy, S**., 'The application of exergy analysis to air cycle plants', Proc. IIR International Conference New Applications of Natural Working Fluids in Refrigeration and Air Conditioning, Hannover, Germany, May 10-13, 1994, pp. 237-246, International Institute of Refrigeration, Paris. - McGovern, James A, 'Exergetic cost analysis of a mechanical exergy recycle', in ENSEC'93, Energy Systems and Ecology, Proceedings of the International Conference, Cracow, Poland, eds. J. Szargut, Z. Kolenda, G. Tsatsaronis, A. Ziebik, July 5-9, 1993, pp. 351-358.
- McGovern, James A. and
**Harte, Shane**, 'Computer simulation of exergy destruction within a reciprocating compressor', Proc. 1992 International Compressor Engineering Conference at Purdue, ed. James F. Hamilton, West Lafayette, Indiana, Purdue University, vol. I, 1992, pp. 309-315. - McGovern, James A. and
**O'Toole, Francis**, 'A virtual-system concept for exergy analysis of flow network plant; Part I: Principles', in ECOS'92, Proceedings of the international symposium on efficiency, costs, optimization and simulation of energy systems, Zaragoza, Spain, ed. Valero, A. and Tsatsaronis, G., American Society of Mechanical Engineers, June 15-18, 1992, pp. 155-160. https://arrow.dit.ie/engschmeccon/48/ - McGovern, James A. and
**O'Toole, Francis**, 'A virtual-system concept for exergy analysis of flow network plant; Part II: Exergetic and exergoeconomic analysis illustration', in ECOS'92, Proceedings of the international symposium on efficiency, costs, optimization and simulation of energy systems, Zaragoza, Spain, ed. Valero, A. and Tsatsaronis, G., American Society of Mechanical Engineers, June 15-18, 1992, pp. 161-166. https://arrow.dit.ie/engschmeccon/49/ - McGovern, James A., 'Compressor rational efficiencies', Proc. Instn. Mech. Engrs., Developments in Industrial Compressors, European conference, 3-4 October 1989, Institution of Mechanical Engineers Conference 1989-10, pp. 59-67.

**Other Publications**

- McGovern, Jim and
**Brian P. Smyth**, ‘Rational Efficiency of a Heat Exchanger’, IRHACE: the Industry Journal for the New Zealand Refrigeration, Heating, Ventilation and Airconditioning Industries, October/November, 2012, pp.12-18 (original working paper made available in ARROW@DIT archive: 3 Oct. 2011). https://arrow.dit.ie/engschmecart/27/

**Theses**

**Smyth, Brian**, 'The Exergy analysis of a multi-effect evaporation unit for seawater desalination', 1997. MSc Thesis, Trinity College, Dublin, Thesis 5540.**Harte, Shane**, 'Thermodynamic design analysis of refrigeration compressors', 1993. PhD Thesis, Trinity College, Dublin, Thesis 3019.**O'Toole, Francis**, 'A new approach to flow constraints in energy analysis', 1992. PhD Thesis, Trinity College, Dublin, Thesis 2777.**O'Toole, Francis**, 'On the application of thermodynamic availability analysis', 1989. MSc Thesis, Trinity College, Dublin, Thesis 1933.